The present invention relates to an exhaust-gas turbocharger.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Internal combustion engines for motor vehicles are increasingly charged by turbochargers to reduce fuel consumption. Fuel consumption is, however, also influenced by the weight of the exhaust system so that turbochargers should be as lightweight as possible but still be robust enough to withstand significant mechanical and in particular thermal stress during operation. Thermally induced stress has an essential influence on the service life of a turbocharger.
German Pat. No. DE 100 22 052 A1 proposes a decoupling of exhaust-conducting components and supporting and sealing outer structures. While the exhaust-conducting components of a turbocharger are exposed to such high thermal stress as to glow during operation, the thermal stress on the sealing outer structure is less. However, also the outer housing is subject to very high stress especially in the regions of attachment onto the bearing housing of a turbocharger. The outer system and outer housing of an exhaust-gas turbocharger normally includes shaped sheet-metal shells which are typically welded via a fusion-welded joint with a bearing flange that serves to secure the exhaust-gas turbocharger to a bearing housing of a turbine wheel. While the bearing housing is cooled to maintain support and thus also the bearing flange is cooled as a result of its contact with the bearing housing, a significant amount of heat is introduced via the outer housing into the bearing flange. The site of highest temperature gradient within the bearing flange is located in proximity of the joint line to the sheet-metal structure of the outer housing and inner housing of the exhaust-gas turbocharger. Geometry and material in particular of this region is weakened by the fusion-welding process, so that this region is subject to fatigue under extreme conditions.
It would therefore be desirable and advantageous to provide an improved exhaust-gas turbocharger to obviate prior art shortcomings.